1. Field of the Invention
The present invention relates to a structure provided with a through hole, which is formed by silicon (Si) semiconductor base plate and others, and also, relates to a method for manufacturing such structure. More particularly, the invention relates to the structure, which is preferably used for a thermal recording head, an ink jet recording head, or the like used for a printer or other printing apparatus, and also, the invention relates to the liquid discharge head and apparatus using such structure.
2. Related Background Art
A structure provided with a through hole is used in various fields. For example, the ink jet recording head used for an ink jet printer or the like that performs recording by discharging ink, uses a structure formed by silicon semiconductor base plate and others provided with a through hole. Hereinafter, by way of example, the description will be made of the structure having a through hole for an ink jet recording head that discharges ink by the application of thermal energy.
For the ink jet recording head that utilizes thermal energy, liquid is given thermal energy generated by heat generative resistive member (heater), thus selectively creating bubbling phenomenon in liquid so as to discharge ink liquid droplet from the discharge port by means of energy exerted by such bubbling. The ink jet recording head of the kind has many numbers of fine heat generating resistive members arranged on a silicon semiconductor base plate or the like in order to enhance recoding density (resolution), and further, each of the discharge ports is arranged to face each of the heat generating resistive members per heat generating resistive member. Then, the driving circuit and peripheral circuits are also arranged on the silicon semiconductor base plate to the heat generating resistive members, respectively.
FIG. 8 is a cross-sectional view that shows the structure of the ink jet recording head of the kind.
As shown in FIG. 8, on one main surface of the silicon base plate 100 of an ink jet recording head, there are laminated a field oxide film (LOCOS oxide film) 101, the BPSG (boro-phospho-silicate-glass) layer 102, which is formed by the non-pressure CVD (chemical vapor development) method, and the silicon oxide film 103, which is formed by the plasma CVD method. Thus, the heat generating resistive member (heater) 110 is formed on the silicon oxide film 103. Further, the discharge port 140 is arranged to face the heat generating resistive member 110. In FIG. 8, only one heat generating resistive member 110 and only one discharge port 140 are represented. Actually, however, several hundreds of heat generating resistive members and discharge ports are provided for an ink jet recording head. These heat generating resistive members are arranged on one single silicon base plate 100 at designated intervals (40 xcexcm, for instance) in the direction perpendicular to the surface of FIG. 8.
Further, in order to protect the heat generating resistive member 110 and others, the silicon nitride film 104, which is formed as a passivation layer by the plasma CVD, is provided for the entire surface of the aforesaid main surface of the silicon base plate 100, including above the heat generating resistive member 110. On the portion of the surface of the silicon nitride film 104, which corresponds to the heat generating resistive member 110, tantalum (Ta) film 105 is formed as a cavitation proof layer in order to prevent the silicon nitride film 110 from being deteriorated by the cavitation phenomenon due to bubbles generated in ink. In this respect, the surface of the main surface of the silicon base plate 100 on the side having no heat generating resistive member 110 formed is covered by thermal oxidation film 106.
The discharge port 140 is formed on the resin covering layer 130 that covers the aforesaid main surface of the silicon base plate 100. There is a space formed between the resin covering layer 130 and silicon nitride film 104, and the tantalum film 105 as well. In this space the liquid (ink) that should be discharged from the discharge port 140 is filled. This space is called a liquid chamber 150.
The ink jet head thus structured is arranged to generate heat when the heat generating resistive member 110 is energized, and create bubbles by such heat in discharge liquid in the liquid chamber 150, hence discharging liquid droplets from the discharge port 140 by the acting force of such bubbles thus created. In order to perform recording continuously, discharge liquid (ink) must be supplied to the liquid chamber 150 in an amount corresponding to the amount of liquid that has been discharged from the discharge port 140. However, the discharge port 140 is arranged near a recording medium, such as paper, and also, the gap between the discharge port 140 and the heat generating resistive member 110 is set minutely. Therefore, it is made difficult to supply discharge liquid into the liquid chamber 150 from the side where the heat generating resistive member 110 is formed for the silicon base plate 100. Here, as shown in FIG. 8, a supply port 120 that penetrates the silicon base plate 100 is provided to enable discharge liquid to flow in the direction indicated by an arrow in FIG. 8 through the discharge port 120 for supplying it into the liquid chamber 150. The supply port 120 is formed with etching the silicon base plate 100.
Now, the thickness of the silicon base plate 100 is several hundreds of xcexcm in general, and if it is intended to etch the silicon base plate 100 for the formation of the supply port 120 from the main surface where the heat generating resistive member 110 is formed, each layer and the heat generating resistive member 110 formed on this main surface are damaged unavoidably, because it takes a long time to complete such etching even under condition established to selectively etch only the silicon base plate 100. Therefore, for the formation of the supply port 120, the silicon base plate 100 is etched from the main surface where no heat generating resistive member 110 is formed. In this case, too, if etching solution should flow into the side where the heat generating resistive member 110 is formed when the penetration of the supply port 120 is completed, there is a fear that damage is given to the heat generating resistive member 110, as well as to each of the other layers. Now, therefore, on the main surface of the silicon base plate 100 on the side where the heat generating resistive member 110 is formed, the layer that becomes an etching stopper is formed in advance on the position where the formation of the supply port 120 is expected. In this manner, it is arranged to prevent etching solution from flowing into the side where the heat generating resistive member 110 is formed.
For the area where the supply port 120 is formed for the one shown in FIG. 8, the filed oxide film 101, the BPSG layer 102, and the silicon oxide film 103 are not provided, but in place thereof, the silicon nitride film 107, which is formed by the reduced pressure CPD method, is provided. The silicon nitride film 107 is patterned and provided so that it is arranged only for the formation area of the supply port 120 and around it. The edge portions thereof are sandwiched between the field oxide film 101 and the silicon oxide film 102. In the formation area of the supply port 120, the silicon nitride film 107 is directly deposited on a thin oxide film 108 of the surface of the silicon base plate 100. The silicon nitride film 104, which is formed by the plasma CVD method, is also formed on the silicon nitride film 107, which is formed by the reduced pressure CVD method.
As described later, in the last stage of etching, the silicon nitride film 107 is exposed to the bottom face of the supply port 120 thus formed. Here, if the silicon nitride film 107 and silicon nitride film 104 are broken or peeled off from the silicon base plate 100 in this stage, etching solution is allowed to leak to the heat generating resistive member 110 side. This is not desirable. Therefore, the silicon nitride film 107 is formed by the reduced pressure CVD method to make the inner stress of the silicon nitride film 107 a tensile stress whereby to prevent the occurrence of peeling as disclosed in the specification of Japanese Patent Application Laid-Open No. 10-181032 (as well as in the specification of the corresponding U.S. Pat. No. 6,143,190).
Here, the structure of the heat generating resistive member 110 will be described. FIG. 9A is a perspective view that schematically illustrates the structure of the heat generating resistive member (heater). FIG. 9B is a circuit diagram that shows the portion that contains the heat generating resistive member and the switching element that drives it.
It is arranged to form the heat generating resistive member 110 by patterning the resistive layer 111 formed by material having electric resistance, such as tantalum silicon nitride (TaSiN), and the aluminum (Al) layer 112 that becomes electrodes in the same shape, and then, part of the aluminum layer 112 is removed so that only resistive layer 111 remains to be present in such portion. This portion where only the resistive layer 111 exists becomes the portion that generates heat when electricity is charged thereon, and becomes the heat generating resistive member 100. In FIG. 9A, after the resistive layer 111 and the aluminum layer 112 are formed on the silicon oxide film 103 in that order, the unwanted parts of both layers are removed so that it shows a U-shaped at first. Then, only the aluminum layer 112 is removed on the portion that becomes the heat-generating portion. In this way, the heat generating resistive member 110 is completed. After that, the silicon nitride film 104 that serves as the passivation layer covers the entire body thereof.
Next, the description will be made of a method for manufacturing an ink jet recording head of the kind. Hereinafter, in order to simplify the description, it is assumed not to consider the thermal oxidation film 106 that should be formed on the side of the silicon base plate 100 where the heat generating resistive member 110 is not formed. Also, in FIGS. 10A, 10B, 10C, and 10D, and FIGS. 11A, 11B, and 11C only the structure of the supply port 120 (the position where it is formed) and circumferential portion thereof is represented.
A method for manufacturing an ink jet recording head using a silicon base plate provided with a through hole is disclosed in the specification of Japanese Patent Application Laid-Open No. 10-181032, for example.
At first, as shown in FIG. 10A, a field oxide film 101 of approximately 700 nm, for instance, is selectively formed on one main surface of a silicon base plate 100. On the portion where no field oxide film 101 is formed, a thin oxide film 108 is formed. Then, as shown in FIG. 10B, the oxide film 108 is removed corresponding to the position where the supply port 120 is formed, so that the silicon surface is exposed accordingly. Further, as shown in FIG. 10C, the poly-silicon layer 121 that serves as the sacrificing layer is formed selectively in a thickness of 200 to 500 nm on the position where the silicon surface is exposed. At this time, the silicon surface having no oxide film 108 formed is arranged to surround the poly-silicon layer 121 completely. After that, as shown in FIG. 10D, the silicon nitride film 107, which is provided by the reduced pressure CVD method, is formed on the position where the supply port 120 is formed and circumferential portion thereof. The thickness of the silicon nitride film 107 is approximately 200 to 300 nm, for example.
After that, as shown in FIG. 11A, the BPSG layer 102, which is provided by the non-pressure CVD method, is formed entirely on the silicon nitride film 107 and the field oxide film 101 in a thickness of 700 nm, for example. Further, entirely thereon, the silicon oxide film 103, which is provided by the plasma CVD method, is formed in a thickness of 1.4 xcexcm. The surface of the silicon oxide film 103 is almost flat. Then, as shown in FIG. 11B, corresponding to the position where the supply port 120 is formed, the silicon oxide film 103 and the BPSG layer 102 are selectively removed in an area slightly larger than the supply port 120. Here, the arrangement should be made so that the edge portions of the part to be removed are positioned above the silicon nitride film 107, but the field oxide film 101 exists below it.
In continuation, the resistive layer 111 and the aluminum layer 112 are formed. Then, as described above, these are patterned in the U-letter form, and with the aluminum layer 112 positioned to be the heat generating portion being selectively removed, the heat generating resistive member 110 is formed on the silicon oxide film 103. Subsequently, as shown in FIG. 11C, the silicon nitride film 104, which becomes a passivation layer, is formed on the entire surface in a thickness of 300 to 800 nm, for example. Then, after the tantalum film 105 that serves as a cavitation proof layer is selectively formed, the silicon base plate 100 on the position where the supply port is formed, and the poly-silicon layer 121 that serves as a sacrificing layer are removed by anisotropic etching from the side of the silicon base plate (from the lower side in FIG. 11C) where no heat generating resistive member 110 of the silicon base plate 100 is provided, thus forming the supply port 120. At this juncture, on the bottom face of the supply port 120, the silicon nitride film 107, which is backed with the silicon nitride film 104, is exposed as the so-called membrane. At the last stage of etching, etching solution is prevented only by this membrane from entering the heat generating resistive member 110 side. Therefore, it should be arranged so that the membrane is not broken or peeled off, because this greatly contributes to enhancing the production yield of recording head.
Lastly, by means of dry etching using fluorine gas or oxygen gas, the silicon nitride film 107 positioned on the bottom face of the supply port 120 and the silicon nitride film 104 are removed. In this way, the base plate used for a recording head, which is provided with the supply port 120 as a through hole for supplying ink or the like, is completed. Thereafter, it should be good enough if only the resin covering layer 130 and discharge port 140 are formed by the known method.
Of the processes described above, the patterning processes (only those which need photomask) for the formation of the supply port 120 are the process in which the oxide film 108 is partly removed as shown in FIG. 10B; the process in which the poly-silicon layer 121 is selectively provided as shown in FIG. 10C; the process in which the silicon nitride film 107 is selectively provided as shown in FIG. 10D; the process in which the BPSG layer 102 and silicon oxide film 103 are removed by etching corresponding to the position of the supply port 120 as shown in FIG. 11B; and the process in which the silicon base plate 100 is etched to from the supply port 120 as shown in FIG. 11C.
On the other hand, as shown in FIG. 9B, one end of the heat generating resistive member 110 is connected with the power-supply source VH of approximately +30 V, and the other end thereof is connected with the drain of a MOS field effect transistor M1 that serves as a drive switching element. Then, the source of the transistor M1 is grounded. The gate thereof is driven when driving pulse is applied. Here, when the driving circuit that includes this transistor M1, and other peripheral circuits is incorporated on the silicon base plate 100, the BPSG layer 102 and the silicon oxide film 103 are formed so as to be an interlayer insulation film, and the silicon nitride film 104 to be a passivation layer. Then, the field oxide film 101 is used for element separation in the formation area of the driving circuit and peripheral circuits thereof.
For the conventional structure, the silicon nitride film 107, which is formed by the reduced pressure CVD method, is intentionally used as a membrane serving as an etching stopper when the supply port 120 is formed. This is because the inner stress of this membrane is tensile stress. In contrast, the inner stress of silicon nitride film 103, which is formed by the plasma CVD method, is compression stress. Conventionally, it has been thought that in order not to allow membrane to be broken or peeled off at the time of etching, a film having tensile stress as a membrane is used so that tension is kept as the membrane, while arranging such film having tensile stress on the silicon base plate side, thus enhancing the bonding power thereof. With this thought, the silicon nitride film 107, which is formed by the reduced pressure CVD method, is used. In other words, it is thought that such problem of breakage and peeling off cannot be solved by use of a film having compression stress.
In the case of the conventional method for manufacturing an ink jet recording head as described above, five photo-masks are needed only for the process in which the supply port is formed even when it is arranged to perform a simultaneous procession of the process in which the silicon base plate is penetrated for the formation of the supply port, and the process in which the heat generating resistive member, the driving circuit and peripheral circuits are formed on the silicon bas plate. In this case, if the other parts (not shown) are also processed, it becomes necessary to use 17 to 18 photo-masks altogether, which makes the processes more complicated. Particularly, the silicon nitride film (the silicon nitride film formed by the reduced pressure CVD method in the aforesaid example) having tensile stress as a membrane is patterned for the provision thereof. As a result, a problem is encountered that numbers of processes are too many.
On the other hand, it has been thought that if the silicon nitride film, which is formed by the plasma CVD method, is used as a membrane, without the formation of silicon nitride film having tensile stress, such problem of breakage or peeling off occurs unavoidably.
Now, therefore, it is an object of the present invention to provide an inexpensive, but highly reliable structure and the method of manufacture therefor by reducing the number of processes.
It is another object of the invention to provide a structure and the method of manufacture therefor, making it possible to enhance more the durability of silicon nitride film constituting a membrane that functions as an etching stopper when a through hole is formed.
It is still another object of the invention to provide a liquid discharge head and a liquid discharge apparatus using such structure.
The present invention is designed with a view to solving the problems discussed above in order to achieve at least one of the objects referred to in the preceding paragraphs.
Now, as a result of assiduous studies made by the inventors hereof, it has been found that even the silicon nitride film, the inner stress of which becomes a compression stress by use of plasma CVD method, can be adopted as membrane when a through hole is formed if only the value of the inner stress (compression stress) thereof is the designated 3xc3x97108 Pa (3xc3x97109 dyn/cm2) or less. With this finding, the present invention is completed.
In other words, the structure of the present invention comprises a semiconductor base plate, and a silicon oxide film and a silicon nitride film formed on a first main surface of the semiconductor base plate, being provided with a through hole penetrating the semiconductor base plate and the silicon nitride film, in which the silicon oxide film is patterned to be arranged on the first main surface of said semiconductor base plate with the exception of the circumferential portion of the through hole, and the silicon nitride film is arranged to be in contact with the semiconductor base plate on the circumferential portion of the through hole on the first main surface of said semiconductor base plate, while covering the silicon oxide film, and the inner stress of the silicon nitride film is a compression stress of 3xc3x97108 Pa or less.
The method of the present invention for manufacturing a structure having a semiconductor base plate, and a silicon oxide film and a silicon nitride film formed on a first main surface of the semiconductor base plate, which is provided with a through hole penetrating the semiconductor base plate and the silicon nitride film, comprises the steps of forming a sacrificing layer on the first main surface of the semiconductor base plate corresponding to the position of the through hole formation; forming a silicon oxide film to cover the entire surface of the sacrificing layer and the first main surface;
patterning the silicon oxide film to enable the first main surface to be exposed on the circumference of the sacrificing layer; forming a silicon nitride film to cover the silicon oxide film and the sacrificing layer with the inner stress thereof being a compression stress of 3xc3x97108 Pa or less; and etching the semiconductor base plate from a second main surface side of the semiconductor base plate to remove the sacrificing layer, and forming a through hole by etching the silicon nitride film.
Now, the inner stress of silicon nitride film is discussed with respect to the present invention. For the invention, it is good enough if the inner stress of silicon nitride film is the compression stress the value of which is 3xc3x97108 Pa or less. It is particularly preferable to make it 5xc3x97107 Pa or more and 2xc3x97108 Pa or less. There is no particular lower limit set for the inner stress, but if the inner stress is made extremely small, there is a fear that the strength of the silicon nitride film becomes lower. Therefore, it is preferable to make it 5xc3x97107 Pa or more practically. It is possible to form a silicon nitride film of the kind by use of plasma CVD method in good condition.
For the present invention, it is preferable that the semiconductor base plate is silicon base plate, and preferably, circuit elements are formed on a first main surface of this silicon base plate. Here, the circuit elements are MOS field effect transistor and others, for example, which are formed by the usual semiconductor manufacturing process on the first main surface. When the circuit elements are formed, it is preferable to execute the process in which the silicon oxide film is patterned simultaneously in the process of froming a contact hole and the process of forming a through hole in the process in which the circuit elements are formed. Further, preferably, the sacrificing layer is formed simultaneously in the process in which the gate electrodes or sourcexc2x7drain electrodes with the same material used for the gate electrodes or sourcexc2x7drain electrodes.
The structure described above is preferably used as a base plate for a liquid discharge head. The base plate of the kind for use of a recording head comprises a semiconductor base plate, a silicon oxide film and a silicon nitride film formed on a first main surface of the semiconductor base plate, and a heat generating resistive member put between the silicon oxide film and the silicon nitride film, being provided with a supply port for supplying liquid penetrating the semiconductor base plate and the silicon nitride film in which the silicon oxide film is pattered to be arranged for the first main surface of said semiconductor base plate with the exception of the circumferential portion of the supply port, and the silicon nitride film is arranged to be in contact with the semiconductor base plate on the circumferential portion of the supply port on the first main surface of said semiconductor base plate, while covering the silicon oxide film, and the inner stress of the silicon nitride film is a compression stress of 3xc3x97108 Pa or less. In this case, the semiconductor base plate is silicon base plate, and it is preferable to form circuit elements on the first surface for driving the heat generating resistive member.
Then, the liquid discharge apparatus of the present invention is provided with the liquid discharge head described above, and a container for containing liquid to be supplied through the aforesaid supply port.